Polymer Dispersed Liquid Crystal (PDLC) is a material with electro-optical response characteristics, mainly working in between scattering state and transparent state and with a certain grayscale. It is made by the following steps: mixing low-molecule liquid crystals with a pre-polymer, polymerizing the obtained mixture under certain conditions to form micron-sized liquid crystal droplets evenly dispersed in macromolecule networks, and then forming PDLC by taking advantage of dielectric anisotropy of liquid crystal molecules. PDLC films are formed by combination of liquid crystals and a polymer and have excellent overall performance. Endowed with outstanding electro-optical characteristics by liquid crystal molecules, PDLC films have attracted great attention and have broad application prospects.
Compared with traditional display devices, PDLC display devices possess many advantages, such as, not requiring a polarizer or an alignment layer, manufacturing procedures being simple, easily made to be large-sized flexible display devices, etc. At present, PDLC display devices have been widely used in fields of optical modulators, temperature-sensitive and pressure-sensitive devices, electronic control glass, light valves, projection display, e-books, etc.
When there is no external voltage, no regular electric field can be formed between PDLC films. Optical axes of liquid crystal particles present themselves with randomly disorder orientations and their effective refractive indexes no do not match the refractive index of the polymer np, in which case light cannot pass through. When there is external voltage, liquid crystal molecules are arranged in a vertical way and their effective refractive indexes no match the refractive index of the polymer np, in which case light can pass through (as illustrated in FIG. 1). Display effects of the PDLC can be influenced by factors including thickness of films, mixing ratio of liquid crystals and the polymer, separation time, temperature, frequency of driving voltage, etc.
However, there are certain technical problems existing in the above-mentioned PDLC display devices. It requires a high driving voltage and has low transmissivity and contrast. Besides, the haze is insufficient when the device is in an off state.